I have a Page with a Table for which its datasource is a relation and needs to be sorted based on fields from another model:
Page
Datasource = Indicators
Table
Datasource = Indicators [one] : MetadataText [many] (relation)
The Table needs to be sorted based on a field from another Model called MetadataField, which has a one to many relation with MetadataText.
I have the datasource of MetadataField sorted. But the content in the Table appears in random order. When I first access the application, the Table is sorted by the order that the records were loaded. After view some records, the sorting of the records changes and keeps changing.
I am using Google Drive tables.
You can easily sort related records by one of the fields that belong to the related record itself, but only once (you'll received those records sorted from server).
But it seems, that you want to sort related records by their related record. App Maker will not be your friend in this case... but javascript will be! Since App Maker loads all related records you can safely sort them on client using javascript:
indicatorsDatasource.load(function() {
indicatorsDatasource.items.forEach(function(indicator) {
indicator.MetadataTexts.sort(function(a, b) {
return /* here goes your sorting logic */;
});
});
});
It will work in O(n * m * log(m)) in case you have n Indicators on the page and every indicator has m associated MetadataTexts. If you want to let users to sort related records by clicking table's header, you'll need to implement that logic on your own. So... all this hassle leads us to alternative solution! What if we decouple related records and introduce separated datasource for them? Having that you'll be able to use full power of App Maker's tables (sorting/paging) with almost no effort. You can take a look at implementation sample in Project Tracker template ViewProject page.
Related
Thanks in advance for your advice!
Background
I’m creating a database to track orders placed by customers.
An ‘Orders’ table stores general details about an order like the customer’s name, order date, and delivery-required date.
A separate ‘Order_Items’ table stores the specific items that the customer has ordered.
The is a one-to-many relationship between the ‘Orders’ table and ‘Order_Items’ table, i.e. one ‘Order’ can have many ‘Order_Items’, but each ‘Order_Item’ must be associated with only one ‘Order’.
Current State
Currently, I have a page where the user creates a new ‘Order’ record. The user is then taken to another page where they can create as many ‘Order_Item’ records as are needed for the order.
Desired State
What I would like to achieve is: When a user creates new ‘Order_Item’ records, it automatically allocates the current ‘Order’ record as the foreign key for the new ‘Order_Item’ record.
What I've Tried So Far
Manual Action By The User: One way of establishing the link between an 'Order' and all of its 'Order_Items' would be to add a drop-down widget which which effectively asks the user something like "Which order number do all of these items belong to"? The user's action would then establish the link between the two tables and associate one 'Order' with many 'Order_Items'. However, my goal is for this step to be handled programatically instead.
Official Documentation: I’ve referred to the offical documentation which was useful, but as I'm still learning I don’t really know exactly what to search for. The prefetch feature appeared promising but does not actually establish a link; it just loads associated records more efficiently.
App Maker Tutorials: I found an App Maker tutorial which creates an HR App where a user can create a list of ‘Departments’, then create a list of ‘Employees’, and then link an ‘Employee’ to a ‘Department’. However, in the example app this connection is established manually by the user. In my desired state I would like the link to be established programatically.
Manual Save Mode:
I’ve also tried switching to manual save mode so that the user has to create a draft ‘Orders’ record and then several draft ‘Order Items’ records and then save them all at once. However, I haven’t managed to make this work. I’m not sure whether the failure of this approach is because 1) I’m try to create draft records on more than one table, 2) I’m just not doing it correctly, or 3) I thought I read somewhere that draft records are deprecated.
Other Ideas
I'm very new to this field and am may be wrong, but I have a feeling I may need to use some scripting to establish the link. For example, maybe I could use a global variable to remember which 'Order' the user creates. Then, for each 'Order_Item' I could use the onBeforeCreate event to trigger a script that establishes the link between the 'Order_Item' and the 'Order' that was remembered from the previously established global variable.
Updated Question
Thanks Markus and Morfinismo for your answers. I have been using both answers with some success.
Morfinismo: I've successfully used the code you directed me to on existing records but cannot seem to get it to work for newly created records.
For example:
widget.datasource.createItem(); // This creates a new record
var managerRecord = app.datasources.Manager.item; // This sets the Manager of the currently selected parent record as a variable successfully.
var teamRecord = app.datasources.Teams.item; // This attempts to set the Manager of the currently selected record as a variable. However, the record that was created in line 1 is not selected. Therefore, App Maker does not seem to know which record this line of code relates to and returns the error Cannot set property ‘Manager’ of null.
// Assign the manager to the team.
teamRecord.Manager = managerRecord; // This successfully assigns the manager but only in cases where the previous line of code was successful (i.e. existing records and not newly created ones).
Do you have any suggestions or comments on how to apply this code to records that are created by the initial line of code in line 1?
I have found the easiest way to create related items for situations such as yours is to actually import a form with the datasource set to Parent: Child (relation) or Parent: Child (relation) (create). So in your case the datasource would need to be set to Order: Order_Items (relation).
You can get this accomplished in two different ways using the form widget wizard:
Option 1:
If your page datasource is set to Order_Items, drag your form on your page.
In the datasource selection section, your datasource in the form widget should default to `Inherited: Order_Items'. Click the 'Advanced' button in the bottom left corner, then from the datasources category find Order as your datasource, then select relations in the next field, and then Order_Items in the next field, choose 'Insert only' or 'Edit' form and then the appropriate fields you want in the form.
Now every item that gets created in that form will automatically be a child record of the currently selected record in your Order datasource.
Option 2:
If your page datasource is set to Order, drag your form on your page.
In the datasource selection section, your datasource in the form widget should default to Inherited: Order. Scroll down in your datasource selection section until you find Order: Order_Items (relation), then choose 'Insert only' or 'Edit' form and then the appropriate fields you want in the form.
Now every item that gets created in that form will automatically be a child record of the currently selected record in your Order datasource.
In your Order model, make sure that the security setting is set appropriately that a user is allowed to create relations of Order_Items in Order. That is the simplest approach in my opinion since you don't have to hard code the parent into your form or client/server scripts. It is automatically based on the currently selected parent, and is essentially doing the same thing that #Morfinismo explained in the client script section.
The comment I placed under your question included a link to the official documentation that explains what you need. Anyways, your question is not clear enough to determine whether you are creating the records via client script or server script, hence this is a very general answer.
To manage relations via client script:
var managerRecord = app.datasources.Manager.item;
var teamRecord = app.datasources.Teams.item;
// Assign the manager to the team.
teamRecord.Manager = managerRecord;
// Changes are saved automatically if the datasource in auto-save mode
// Add a team member to a Manager's team.
// Note: Retrieve Members on the client before proceeding, such as by using prefetch option in datasource - datasources Team -> Members)
var engineerRecord = app.datasources.TeamMember.item;
teamRecord.Members.push(engineerRecord);
To manage relations via server script:
// Get the record for the Team to modify.
var teamRecord = app.models.Teams.getRecord("team1");
// Assign a manager to the Team.
var managerRecord = app.models.EmployeeDB.getRecord("manager1");
teamRecord.Manager = managerRecord;
// Note: The new association is not saved yet
// Assign a team member to the Team.
var engineerRecord = app.models.EmployeeDB.getRecord("engineer1");
teamRecord.Members.push(engineerRecord);
// Save both changes to the database.
app.saveRecords([teamRecord]);
The above information is taken directly from the official documentation, which like I said, I referred to in the comment I placed under your question.
I'm working on a website that mostly displays items created by registered users. So I'd say 95% of API calls are to read a single item and 5% are to store a single item. System is designed with AWS API Gateway that calls AWS Lambda function which manipulates data in DynamoDB.
My next step is to implement voting system (upvote/downvote) with basic fetaures:
Each registered user can vote only once per item, and later is only allowed to change that vote.
number of votes needs to be displayed to all users next to every item.
items have only single-item views, and are (almost) never displayed in a list view.
only list view I need is "top 100 items by votes" but it is ok to calculate this once per day and serve cached version
My goal is to design a database/lambda to minimize costs of AWS. It's easy to make the logic work but I'm not sure if my solution is the optimal one:
My items table currently has hashkey slug and sortkey version
I created items-votes table with hashkey slug and sortkey user and also voted field (containing -1 or 1)
I added field votes to items table
API call to upvote/downvote inserts to item-votes table but before checks constraints that user has not already voted that way. Then in second query updates items table with updated votes count. (so 1 API call and 2 db queries)
old API call to show an item stays the same but grabs new votes count too (1 API call and 1 db query)
I was wondering if this can be done even better with avoiding new items-votes table and storing user votes inside items table? It looks like it is possible to save one query that way, and half the lambda execution time but I'm worried it might make that table too big/complex. Each user field is a 10 chars user ID so if item gets thousands of votes I'm not sure how Lambda/DynamoDB will behave compared to original solution.
I don't expect thousands of votes any time soon, but it is not impossible to happen to a few items and I'd like to avoid situation where I need to migrate to different solution in the near future.
I would suggest to have a SET DynamoDB (i.e. SS) attribute to maintain the list of users who voted against the item. Something like below:-
upvotes : ['user1', 'user2']
downvotes : ['user1', 'user2']
When you update the votes using UpdateExpression, you can use ADD operator which adds users to SET only if it doesn't exists.
ADD - Adds the specified value to the item, if the attribute does not
already exist. If the attribute does exist, then the behavior of ADD
depends on the data type of the attribute:
If the existing data type is a set and if Value is also a set, then
Value is added to the existing set. For example, if the attribute
value is the set [1,2], and the ADD action specified [3], then the
final attribute value is [1,2,3]. An error occurs if an ADD action is
specified for a set attribute and the attribute type specified does
not match the existing set type. Both sets must have the same
primitive data type. For example, if the existing data type is a set
of strings, the Value must also be a set of strings.
This way you don't need to check whether the user already upvote or downvote for the item or not.
Only thing you may need to ensure is that the same user shouldn't be present on upvote and downvote set. Probably, you can use REMOVE or ConditionExpression to achieve this.
I was wondering if there is any way to populate a table using two different records. My records have the same primary keys, but when I am adding the specific fields to my grid I have this error:
More than one data (key) in one scroll.
I tried to make a Control view field in my primary record, and then refer the new record fields as relative fields but in this case the data is not populating in my grid. Any help or hint will be much appreciated.
I've only done this where the 2nd record is a Derived/Work record.
Can you create a view that combines both records, and put the view in the grid? FYI, peoplesoft let's you update the data in a view, which is not typical in an oracle db system.
Ok guys finally after all discussion, and much try rounds I figured out how to do this.
You need to add a draw a grid beside your old grid and populate it with a new record, which has dynamic view (dynamic sql). The only important case there, is you need to make sure the order of your fields in your records, are in the same order of your fields in the SELECT statement of your sql. Otherwise you will see
an SQL error
.
Try to make a field as display control field which is acting as primary key for its native table and as Foreign key for some other record.. A field needs to be made related if is being fetched from some other record... that is from the record which is not under current consideration. I think this way one can fetch data into grid or scroll respectively from multiple records.
In my application i added all data into table view. Then I need entire row by using search operation.
Searching is based upon any data like search by RegisterNo or search by Name. By entering RegisterNo it Should display entire row related to RegisterNo.
To do search operation in a TableView, what I've done is to add a notion of filters.
For example if you want to filter by name, each time your name query change, you filter all your data and let on the table only those who match your query.
You always keep the full data to execute your query on it, but to display it use an other list.
with that I'm able to have lot of filters at the same moment and my view refresh in real time
I have an admin section for many databases set up using Dynamic Data. When the user logs in, they are presented with a list of databases that they have access to modify (this list is kept in a separate database that is tied to the person's login information and also lists the tables they are allowed to see). Upon clicking on the database, a list of tables is then shown in a second gridview on the same default.aspx page for the Dynamic Data site.
I have found a way to limit the tables shown to the ones corresponding to the database entries of allowed tables, however, upon viewing the table entries, any foreign key associations to tables they do not have access to show up with the dynamic data hyperlinks that take you over to those tables directly.
Soooo, if you are still with me, thank you. My thought was to do a check in the global.asax file where the metamodels are bound and just not scaffold the tables that are supposed to be inaccessible. Can this be done programmatically? I would post some code but I'm not really sure what would be needed. Here is where I'm thinking I can make an edit:
foreach (var table in metaModel.Value.Tables)
{
var tablePermission = authorizedTables.Any(p => p == table.Name);
if (tablePermission) continue;
//Next lines are possible ways in?
var canThisBeSetSomehow = table.Attributes.OfType<ScaffoldTableAttribute>().FirstOrDefault();
table.Scaffold = false;
}
Assume that "authorizedTables" is a string[] that holds my table names in the above scenario. Is there a way to take the metamodel and edit it so that the remaining tables are inaccessible on a per user basis?